A kinematic study of luno-triquetral dissociations

In vivo analysis of carpal kinematics and comparative review of the literature

PURPOSE

Techniques have been developed very recently with which it is possible to quantify accurately in vivo 3-dimensional (3-D) carpal kinematics. The aim of this study was to evaluate the feasibility of our novel 3-D registration technique by comparing our data with data found in the literature.

METHOD

The right wrists of 11 healthy volunteers were imaged by spiral computed tomography (CT) during radial-ulnar deviation and 5 of those wrists were imaged also during flexion-extension motion. With a matching technique relative translations and rotations of the carpal bones were traced. We compared our in vivo results with data presented in the literature.

RESULTS

We found our in vivo data largely to concur with in vitro data presented in the literature. In vivo studies revealed only larger out-of-plane motions within the proximal carpal row than described in most in vitro studies. In vivo studies also showed larger interindividual variations.

CONCLUSIONS

A single functional model of carpal kinematics could not be determined. We expect that in vivo 3-D CT studies on carpal kinematics, especially when applied to dynamic wrist motion, will have future diagnostic applications and provide information on long-term results of surgical interventions.

Arthroscopic repair of dorsal radiocarpal ligament tears

Various authors have highlighted the importance of the dorsal radiocarpal (DRC) ligament in normal carpal kinematics. It is a secondary stabilizer of the lunate and has a role in midcarpal stability. Disruption of the DRC ligament has been implicated in the development of static VISI and DISI deformities, prompting some authors to perform an open reattachment of the dorsal capsule if there is an associated scapholunate ligament tear. The management of these tears is still evolving. The contribution of a DRC ligament tear to the development of wrist pain remains uncertain when combined with additional wrist pathology. An isolated DRC ligament tear was responsible for chronic dorsal wrist pain in 2 patients. A previously undescribed inside-out repair method of the DRC ligament using a volar wrist portal was successful in relieving the pain. Recognition of this condition and further research into treatment methods is needed.

Scaphoid kinematics in vivo

The purpose of this study was to quantify 3-dimensional (3-D) in vivo scaphoid kinematics during flexion-extension motion (FEM) and radial-ulnar deviation (RUD) of the hand. The right wrists of 11 healthy volunteers were imaged by spiral computed tomography during RUD and 5 of those wrists also during FEM. With a matching technique, relative translations and rotations of the scaphoids were traced. Our results showed a broad spectrum of kinematic patterns of the scaphoid during RUD, with small intercarpal motions within the proximal carpal row. Some scaphoids rotated basically around the flexion-extension axis only whereas others rotated almost entirely around the deviation axis during RUD. During FEM we found highly uniform scaphoid motion patterns with large intercarpal motions within the proximal carpal row. These findings suggest that current theories cannot sufficiently explain wrist kinematics and stress the need for more in vivo studies on 3-D carpal kinematics.

Wrist kinetics after luno-triquetral dissociation: the changes in moment arms of the flexor carpi ulnaris tendon

Wrist biomechanics after luno-triquetral (LT) dissociation is important for understanding the clinical sequelae of the disease and for determining its treatment options. The LT interosseous ligament plays an important role in stabilizing the joint and damage to the ligament would be expected to significantly increase moment arms of tendon of the flexor carpi ulnaris (FCU), the principal ulnar wrist flexor. We investigated the changes in moment arms of FCU tendon after various amounts of sectioning of the ligaments proven to be associated with LT dissociation. In six fresh frozen cadaveric upper extremities, excursions of the FCU tendon were recorded simultaneously with wrist joint angulation during wrist flexion-extension and radioulnar deviation. Tendon excursions were measured in intact wrists, in wrists with sectioning of the dorsal portion of the LT interosseous ligament, in wrists with sectioning of the entire LT interosseous ligament, and finally in wrists with further sectioning of the dorsal radiotriquetral and intercarpal ligaments. Moment arms of the tendon were calculated from tendon excursions and joint motion angulations and expressed as percentage changes from those in the intact wrist. During wrist flexion-extension, moment arms of the FCU tendon after sectioning of the entire LT interosseous ligament and after sectioning of the two capsular ligaments were 112 +/- 7% and 114 +/- 8%, respectively; these values were significantly greater than those in the intact wrist. During radioulnar deviation, the moment arms were 114 +/- 11% after sectioning of the dorsal portion of the LT interosseous ligament, 134 +/- 15% after sectioning of the entire ligament, and 153 +/- 18% after sectioning of the capsular ligaments, again being significantly greater than the normal wrist. Increase in moment arms of the FCU tendon after loss of integrity of the LT interosseous ligament and dorsal capsular ligaments may contribute to clinical sequelae of LT dissociation and difficulty in treating this disorder.

Three-dimensional carpal kinematics in vivo

OBJECTIVE

The purpose of this study was to accurately quantify three-dimensional in vivo kinematics of all carpal bones in flexion and extension and radial and ulnar deviation.

DESIGN AND METHODS

The right wrists of 11 healthy volunteers were imaged by spiral CT with rotational increments of 5 degrees during ulnar-radial deviation and of five of them also during flexion-extension motion. One regular-dose scan was used and the subsequent scans during wrist motion were performed with one-tenth of the regular dose. A three-dimensional matching technique using the internal structure of the bones was developed to trace the relative translations and rotations of the carpal bones very accurately.

RESULTS

Most of our results are in concordance with previously published in vitro data. We could, among others, substantiate proof to the statement that there is more than one kinematic pattern of the scaphoid. Furthermore, we could accurately describe small adaptive intercarpal motions in vivo of the distal carpal row.

CONCLUSIONS

To our knowledge, this is the first time the three-dimensional in vivo kinematics of all eight carpal bones is quantified accurately and non-invasively.

RELEVANCE

Kinematics of an injured wrist can be compared to these reference data. It may become possible that in this way a ligament lesion can be detected with high specificity and sensitivity, and that no other diagnostic modality will be needed. With these data we made animations with which the complex movements of the bones during different motions of the wrist can be viewed. In the future it may become possible that this analysis provides valuable information on the long-term results of operative interventions and possibly predicts results of operative techniques.

Wrist arthroscopy through a volar radial portal

PURPOSE

To quantitatively describe the neurovascular relationships of a volar radial wrist arthroscopy portal and to evaluate whether volar wrist arthroscopy identified additional pathology of the dorsal capsular structures and the palmar region of the scapholunate interosseous ligament that was not seen through the dorsal portals.

TYPE OF STUDY

This study was an anatomic study and retrospective chart review.

METHODS

Cadaver dissections established the neurovascular anatomy of the volar radial portal. Measurements were taken from the portal to the radial artery and its superficial palmar branch; the superficial radial nerve, the median nerve, and its palmar cutaneous branch; and the pronator quadratus. A dorsal capsulotomy was performed to assess the ligamentous interval. A chart review of 30 patients in whom a volar radial portal was used was performed. Intraoperative pathology identified through volar wrist arthroscopy that was not visible through a dorsal portal was recorded. Postoperative neurovascular complications were noted.

RESULTS

There was a greater than 3 mm safe zone surrounding the portal that was free of any neurovascular structures. There were no complications from the use of the portal. Additional pathology that was not visible from a dorsal portal was identified in 10 cases. This included 1 case of hypertrophic synovitis of the dorsal capsule, 1 patient with an avulsion of the radioscapholunate ligament, 1 patient with a tear restricted to the palmar region of the scapholunate interosseous ligament, and 7 patients with tears of the dorsal radiocarpal ligament.

CONCLUSIONS

This study provides a safe, standardized approach to the volar radial aspects of the radiocarpal and midcarpal joints. Volar wrist arthroscopy identified additional pathology of the palmar scapholunate interosseous ligament and dorsal capsular structures in 30% of the patients. The volar radial portal should be considered for inclusion in the arthroscopic examination of any patient with radial-sided wrist pain.

The effect of sectioning the dorsal radiocarpal ligament and insertion of a pressure sensor into the radiocarpal joint on scaphoid and lunate kinematics

The role of the dorsal radiocarpal wrist ligament has been the subject of several investigations. Several biomechanical studies have used sensors inserted dorsally into the wrist joint to evaluate its pressure distribution. The purpose of this study was to evaluate whether a dorsal capsulotomy that sections the dorsal radiocarpal ligament or insertion of a flexible pressure sensor alters scaphoid or lunate kinematics. Eight cadaver upper extremities were instrumented with motion sensors and placed in a wrist joint simulator. Each arm was moved through continual cycles of wrist flexion/extension and radial/ulnar deviation. Motion data were obtained in the intact state, after a capsulotomy, and after insertion of the sensor. We found that either a dorsal capsulotomy sectioning the dorsal radiocarpal ligament or insertion of the pressure sensor alters scaphoid and lunate kinematics during dynamic wrist motion. This study supports the clinical belief that this dorsal wrist ligament should be spared during surgical approaches to the carpus.

Lunotriquetral arthrodesis using cancellous bone graft

Previous reports of lunotriquetral arthrodesis suggest relatively low rates of primary fusion without the use of permanent fixation and/or prolonged immobilization. We performed 26 lunotriquetral arthrodeses in 24 patients with a technique using cancellous bone graft to fill a biconcave space created in the adjoining bones with parallel K-wire fixation. The indications included symptomatic lunotriquetral instability and degenerative arthritis. All patients received conservative treatment before surgery. Primary fusion was achieved in all wrists in an average of 50 days. Postoperative wrist flexion/extension averaged 77%/80% of unaffected sides. Radial/ulnar deviation averaged 95%/91% of unaffected sides. Pain relief was good or very good in 83%. Eight-eight percent returned to the workforce. This study shows reliable, effective results with a technique that adheres to the principles of intercarpal arthrodesis and avoids permanent internal fixation.

Advances in the in vivo measurement of normal and abnormal carpal kinematics

This article presents the development of an in vivo, three-dimensional methodology using markerless bone registration for examining the normal and abnormal kinematics of the wrist carpal bones. The resulting descriptions of three-dimensional kinematics from healthy patients and patients with documented unilateral scapholunate interosseous ligament injuries are briefly presented.

Arthroscopic capsulodesis of the lunotriquetral joint

A case series consisting of 20 consecutive patients with persistent ulnar-sided mechanical wrist pain, lunotriquetral interosseous (LTIOL) ligament tears resulting in joint incongruity and increased laxity, and traumatic triangular fibrocartilage complex (TFCC) tears was reviewed. Each patient underwent an arthroscopic reduction and internal fixation (ARIF) of the lunotriquetral joint, arthroscopic disk-carpal (disklunate-ulnocapitate-disktriquetral, DL-UC-DT) ligament plication, and TFCC repair or débridement. There were 12 right wrists and 8 left wrists, of which 12 were dominant. The mean patient age was 33 years; 7 patients had workers' compensation claims and 2 had legal claims. Fourteen patients recalled a specific injury mechanism, such as hyperextension or rotation. The accompanying traumatic TFCC tears were peripheral in 15 and linear radial in 6 patients (one patient had concomitant peripheral and radial linear tears), and in 6 cases, the palmar ulnocarpal extrinsic ligaments were partially torn. The mean preoperative modified Mayo Wrist Score was 50, and at a mean of 3.1 years after surgery, the score had increased to 88. There were 13 excellent, 5 good, and 2 fair results. Four patients had complications, including transient tenderness along the extensor carpi ulnaris and persistent neuritis of a dorsal branch of the ulnar nerve. Overall wrist comfort and function, as indicated by the modified Mayo Wrist Scores, improved after arthroscopic stabilization of ulnar-sided wrist injuries (pinning of the lunotriquetral joint, disk-carpal ligament plication, and TFCC repair or débridement).

Arthroscopy of the wrist for trauma

Over the last decade wrist arthroscopy has proven itself to be a very useful procedure in the management of both bony and soft tissue injuries of the region. Access is achieved through the potential spaces between the dorsal extensor tendons, overlying the joint. Distraction of the wrist joint and instillation of fluid distends the cavity to allow inspection and therapeutic procedures. The radio-carpal and mid-carpal, as well as distal radio-ulna articular surfaces and associated intrinsic and possibly some extrinsic carpal ligaments, are well visualized and dynamic testing of structures is possible. In terms of diagnosis of carpal ligament and triangular fibrocartilage complex (TFCC) injuries it consistently outperforms imaging modalities available. It has also lead to a greater appreciation of the high incidence of occult chondral and ligamentous injury that may co-exist with intraarticular fractures, although the significance of these injuries is debated. Therapeutically it has proven useful in the reconstruction of the articular surface and in the treatment of chondral, intrinsic carpal and TFCC injuries. Results here have been generally comparable to established managements.

Kinematic accuracy of three surface registration methods in a three-dimensional wrist bone study

The use of registration techniques to determine motion transformations noninvasively has become more widespread with the increased availability of the necessary software. In this study, three surface registration techniques were used to generate carpal bone kinematic results from a single cadaveric wrist specimen. Surface contours were extracted from specimen computed tomography volume images of the forearm, carpal, and metacarpal bones in four arbitrary positions. Kinematic results from each of three registration techniques were compared with results derived from multiple spherical markers fixed to the specimen. Kinematic accuracy was found to depend on the registration method and bone size and shape. In general, rotation errors of the capitate and scaphoid were less than 0.5 deg for all three techniques. Rotation errors for the other bones were generally less than 2 deg, although error for the trapezoid was greater than 2 deg in one technique. Translation errors of the bones were generally less than 1 mm, although errors of the trapezoid and trapezium were greater than 1 mm for two techniques. Tradeoffs existed in each registration method between image processing time and overall kinematic accuracy. Markerless bone registration (MBR) can provide accurate measurements of carpal kinematics and can be used to study the noninvasive, three-dimensional in vivo kinematics of the wrist and other skeletal joints.

Lunotriquetral instability: diagnosis and treatment

Isolated injury of the lunotriquetral interosseous ligament complex and associated structures is less common and is poorly understood compared with the other proximal-row ligament injury, scapholunate dissociation. The spectrum of injuries ranges from isolated partial tears to frank dislocation, and from dynamic to static carpal instability. The diagnosis may be difficult to establish because of the many possible causes of ulnar-sided wrist pain and the often normal radiographic appearance. The mechanism of injury is variable and includes attrition by age, positive ulnar variance, and perilunate or reverse perilunate injury. Appropriate treatment requires assessment of the degree of instability and the chronicity of the injury. Options include corticosteroid injection, immobilization, ligament repair, ligament reconstruction with tendon grafts, limited intercarpal arthrodesis, and ulnar shortening.

Transducer user syndrome: an occupational hazard of the ultrasonographer

Since no study to date has assessed the prevalence of scanning-related disorders amongst sonographers in Obstetrics and Gynecology, we distributed a survey to all trained personnel in our ultrasound division. We evaluated the correlation between injuries sustained in the workplace, and factors such as age, gender, work load and intensity, scanning techniques, previous medical problems, and physical activity. Injuries included one or more of the following: carpal tunnel syndrome; carpal instability; tendinitis; back, shoulder, and neck pain; tingling and/or numbness in the extremities; weakness; and motion restriction. Of the 44 respondents, 29 (65%) have experienced some type of injury or symptom over the course of their scanning career. Five (12%) reported having missed work because of their symptoms, 15 (34%) have received orthopedic treatment (medication or physiotherapy), two (4.5%) have been diagnosed with carpal tunnel syndrome, and one (2.3%) with carpal instability based on electrophysiological examinations. These results demonstrate that ultrasound scanning in Obstetrics and Gynecology may pose an occupational risk for doctors and technicians.

The dorsal ligaments of the wrist: anatomy, mechanical properties, and function

The purpose of this study was to examine the anatomy and mechanical properties of the dorsal radiocarpal (DRC) and dorsal intercarpal (DIC) ligaments of the wrist and to better understand the functional design of the dorsal ligaments. The DRC ligament was consistently found to originate from the dorsal margin of the distal radius and extended ulnar obliquely and distally. Its radial fibers attached to the lunate and lunotriquetral interosseous ligament. The DRC ligament then inserted onto the dorsal tubercle of the triquetrum. The DIC ligament originated from the triquetrum and extended radially and attached onto the lunate, inserted into the dorsal groove of the scaphoid, and then extended to the trapezium. The DRC and DIC ligaments together, in their lateral V configuration, act effectively as a dorsal radioscaphoid ligament that has the ability to vary its length by changing the angle between the 2 arms of the V. The DRC-DIC ligaments' lateral V configuration allows normal carpal kinematics while maintaining its indirect dorsal stabilizing effect on the scaphoid throughout the range of motion of the wrist.

Noninvasive technique for measuring in vivo three-dimensional carpal bone kinematics

Our present knowledge of the three-dimensional kinematic behavior of skeletal joints has been largely acquired with cadaveric models and use of invasive monitoring. In the wrist, the small size and complex motion of the carpal bones present a difficult challenge for implanted internal or external marker systems. This paper describes a technique for quantifying the three-dimensional kinematics of the wrist and carpal bones in vivo using noninvasive computed tomographic imaging. An error analysis employing a cadaveric specimen suggests that noninvasive carpal kinematics can be measured with an accuracy within 2 degrees of rotation and 1 mm of translation along a helical axis of motion. The in vivo application of this technique is illustrated with a single normal individual. Potential applications include the quantification of normal wrist motion, analysis of pathomechanics, and evaluation of surgical intervention. The technique is also applicable to other joints and imaging modalities.

The effects of wrist distraction on carpal kinematics

Changes in carpal kinematics under wrist distraction were studied in fresh cadaveric specimens. A magnetic tracking device measured kinematic motions of the scaphoid, lunate, and third metacarpal relative to the fixed radius in 3 planes of passive motion (coronal, sagittal, and "dart throwers") under progressive distraction loads. The change in percent contribution of the radiocarpal and midcarpal joints was calculated. Radiocarpal motion during extension was decreased as increasing traction was applied, but it increased with flexion. Motion of the scaphoid relative to the lunate was smaller in the oblique plane, resulting in less radiocarpal motion than in the sagittal plane. In the coronal plane, traction had little effect on radial deviation, but ulnar angulation of the scaphoid was greater with ulnar deviation of the wrist. These results suggest that different degrees of tension exist in the palmar and dorsal ligaments with the wrist under traction and during different planes of wrist motion. If wrist motion is desired during fixed traction, such as used clinically with external fixation, the dart-throwers motion (wrist extension with radial deviation and wrist flexion with ulnar deviation) appears to have the least impact on radiocarpal motion. If greater radiocarpal motion is desired, however, such as during postoperative mobilization, flexion-extension and radioulnar deviation will create more radiocarpal motion than the dart-thrower's motion.

A biomechanical study of the human cricoarytenoid joint

OBJECTIVES/HYPOTHESIS

To develop a model to investigate the biomechanics of the cricoarytenoid joint and establish stiffness, laxity, and range of motion of the cricoarytenoid joint in adult human larynges.

STUDY DESIGN

Laboratory investigation of freshly frozen larynges from adult humans, measuring the stiffness, laxity, and range of motion in intact and injured cricoarytenoid joints.

METHODS

Eight normal-appearing frozen cadaver larynges from adult humans were studied. The cricoid cartilage was fixed to a load cell sensitive to forces in three dimensions. A probe was rigidly fixed to the arytenoid cartilage and attached to a frame to allow active rotation, rocking, and gliding of the arytenoid. A computer program simultaneously recorded forces generated by these motions and tracked the motion of the arytenoid in three dimensions. The joint was studied before and after injury to the posterior cricoarytenoid ligament, and the joint surfaces were digitized after completion of these studies.

RESULTS

A successful method of evaluating the biomechanical properties of the cricoarytenoid joint was developed. Comparing intact and injured joints confirmed that laxity and range of motion increased during rocking, gliding, and rotational motion when the cricoarytenoid ligament had been divided. Stiffness measurements for rocking, rotation, and gliding also were documented.

CONCLUSIONS

The model of study introduced in this report provides a significant and unique method of investigating the biomechanics of the cricoarytenoid joint, allowing insight into the basic joint characteristics and alteration in joint biomechanics related to injuries and surgical procedures. Dividing the cricoarytenoid ligament increases laxity and range of motion in sagittal rocking, gliding, and axial rotation. Secondary constraints on the joint provide significant stiffness of greater degrees of displacement. Further studies should provide insight into the significant secondary elements supporting the joint and into the mechanisms of cricoarytenoid injuries, as well as the effect of surgical procedures on the cricoarytenoid joint.

Ligamentous injuries of the wrist in the athlete

Wrist instability most commonly results from ligamentous disruption between bones of the proximal carpal row. Scapholunate and lunotriquetral dissociation are forms of this instability pattern. Carpal instability can also occur due to loss of the normal ligamentous restraints between the carpal rows. Ulnar midcarpal instability is an example of this pattern. The treatment of wrist instability depends on the specific type and degree of carpal disruption and the presence or absence of degenerative changes. Options include soft-tissue reconstruction, partial wrist fusion, limited carpal bone excision, or a combination of methods.

Kinematics of the capitolunate joint in the sagittal plane. A new method based on reference points and triangulation

A new method of assessing capitolunate alignment is presented. Three anatomical carpal reference points were evaluated on lateral radiographs using triangulation. Connecting these three points forms a triangle with dorsal, palmar and somewhat vertical sides. One hundred normal lateral wrist radiographs were measured. The overall dorsal limb (DL) to palmar limb (PL) ratio was found to be 0.74 (SD 0.07) over a range of 40 degrees extension to 42 degrees flexion. As the DL to PL ratio approached 1.0, a dorsal intercalated segment instability (DISI) deformity developed. Conversely, as the DL to PL ratio approached 0.5, a palmar intercalated segment instability (PISI) occurred. This method appears useful for evaluating static lateral radiographs for intercalary carpal alignment and possibly instability.

Lunotriquetral ligament properties: a comparison of three anatomic subregions

The physical attributes of 3 subregions of the lunotriquetral ligament were tested in a computer-controlled multiaxis testing machine using 12 specimens. This allowed measurement of forces, moments, and displacements when ligaments were subjected to distraction, dorsopalmar translation, proximal-distal translation with a 20 N limit, and rotation with a 0.5 Nm limit. After an intact test run, selected subregions were cut randomly. Together with an additional 12 bone-ligament-bone complexes, specimens were tested to failure with servohydraulic load at 5 mm/s. The palmar subregion was thickest (2.3 +/- 0.3 mm), the dorsal and proximal progressively less. Intact rotational displacement was 35 degrees +/- 5.1 degrees, dorsopalmar displacement was 1.6 +/- 0.4 mm and 1.2 +/- 0.5 mm, respectively, proximal-distal displacement was 1.8 +/- 0.5 mm and 1.3 +/- 0.5 mm, respectively, and distractional displacement was 0.3 +/- 0.1 mm. The dorsal subregion provided 62.3% +/- 27.1% of the rotational resistance. The palmar subregion resisted 67.3% +/- 14.1% of palmar translation, while with dorsal translation both regions resisted equally. Rotational displacement increased 15.3 degrees +/- 5.6 degrees after dorsal subregion sectioning. The palmar component failure force was 301 +/- 36 N; the dorsal, 121 +/- 42 N; and the proximal, 64 +/- 14 N.

The lunotriquetral joint: kinematic effects of sequential ligament sectioning, ligament repair, and arthrodesis

This experiment was conducted to study the effects of sequential sectioning of the ligaments of the lunotriquetral (LT) joint and the effects of simulated repair or arthodesis on kinematics of the wrist joint using an x-ray stereophotogrammetric technique. A 3-dimensional coordinate software program calculated relative motion between bodies as screw axis displacement and rotation about each axis. Sectioning of the proximal and dorsal component of the LT ligament had little effect on carpal kinematics, but sectioning of the proximal and palmar components of the ligament resulted in flexion of both the lunate and triquetrum, producing a volar intercalated segment instability (VISI) pattern. The triquetrum supinated away from the lunate after sectioning of the entire LT ligament. Greater VISI occurred after sectioning the dorsal radiotriquetral and scaphotriquetral ligaments. Progressive destabilization of the LT joint results in increasing kinematic alterations; however, these may not exactly mimic the clinical situation. Moving the wrist through 1,000 cycles increased the instability. Dorsal repair of the LT ligament realigned the lunate and triquetrum, and LT fusion corrected triquetral supination. The latter, however, resulted in overcorrection into extension, which prevented a full wrist extension. The repair used may be insufficient to restore the palmar ligamentous integrity. Lunotriquetral arthodesis was difficult to simulate, providing some insight into the cause of clinical nonunions. Severe VISI is not correctable by repair or arthrodesis and requires further study using reconstructive procedures not discussed here.

Feasibility of using a magnetic tracking device for measuring carpal kinematics

While several different methods have been used to measure carpal kinematics, biplanar radiography is generally considered to be the most accurate and popular one. However, biplanar radiography is tedious and so only pseudo-dynamic kinematics can be measured. Recently, magnetic tracking system has been developed for the measurement of joint kinematics which is versatile and easy to use and so the possibility of measuring motions dynamically. In this study, the capability of a magnetic tracking device to accurately measure carpal kinematics was investigated by comparing it with biplanar radiography. The kinematics of the third metacarpal, scaphoid, and lunate in five fresh cadaveric specimens were measured using both methods as the wrists were placed in eight positions. The finite screw rotation of each bone with respect to the distal radius during selecting the seven wrist motions was calculated for both measuring techniques and compared. In general, the kinematics for all three bones measured by using either magnetic tracking device or biplanar radiography was identical and showed no statistical difference. The averaged differences ranged from 0.0 to 2.0 degrees. These differences were due to the potential effect of the weight of the sensors and the interference of the attaching rod to the surrounding tissue. It is concluded that the application of the magnetic tracking device to carpal kinematics is warranted, if proper technical procedures as suggested are followed.

Normal kinematics of carpal bones: a three-dimensional analysis of carpal bone motion relative to the radius

Normal carpal kinematics were studied in 22 cadaver specimens using a biplanar radiography method. The kinematics of the trapezium, capitate, hamate, scaphoid, lunate, and triquetrum were determined during wrist motion in sagittal and coronal planes. The results were expressed using the concept of the screw displacement axis and converted to describe the magnitude of rotation about and translation along three axes (X-axis: pronation-supination axis, Y-axis: flexion-extension axis, and Z-axis: radial-ulnar deviation axis) commonly used for the wrist. The orientation of these axes is expressed relative to the radius. Within the proximal carpal row, considerable differences of carpal behavior around the Y-axis were observed during sagittal plane motion of the wrist. The scaphoid exhibited the greatest magnitude of rotation, and the lunate the least. The magnitude of rotation of the carpal bones around the X-axis during sagittal plane motion of the wrist was small. The proximal carpal bones exhibited some ulnar deviation in 60 degrees of wrist flexion. During coronal plane motion of the wrist, the magnitude of radial-ulnar deviation of the distal carpal bones was mutually similar and generally of a greater magnitude than that of the proximal carpal bones. The proximal carpal bones experienced some flexion during radial deviation of the wrist and extension during ulnar deviation of the wrist. Translation was generally minimal in all carpal bones throughout wrist motion. This study reports results from the largest cadaver wrist kinematics study completed to date. The accuracy of the current method was improved when compared to previous studies. A sufficient number of specimens to allow statistical comparison was used and minimal interspecimen variability was noted. This study enabled a precise description of quantitative analyses of normal carpal kinematics relative to the radius.

Biomechanical changes of the wrist flexor and extensor tendons following loss of scaphoid integrity

Loss of integrity of the scaphoid may change the motion center of the entire carpus, and deformities from scaphoid fractures may alter the location of motor tendons of the wrist, thus altering their biomechanics. The goal of this study was to clarify biomechanical changes in these tendons following loss of scaphoid integrity. Excursions and moment arms of the principal flexor and extensor tendons of the wrist were investigated in seven cadaveric upper extremities in intact wrists after simulation of scaphoid waist fracture and after removal of the proximal scaphoid. Excursions of the flexor carpi radialis and ulnaris, extensor carpi radialis longus and brevis, and extensor carpi ulnaris tendons were measured with rotary potentiometers during wrist flexion-extension and radioulnar deviation. Simultaneously, wrist joint angulation was recorded. Moment arms of the tendons were derived from tendon excursions and joint motion. After scaphoid fracture, the moment arms of the flexor carpi radialis and extensor carpi ulnaris tendons increased significantly during wrist flexion-extension, whereas the moment arms of the extensor carpi radialis longus and brevis tendons decreased significantly. After proximal scaphoid excision, the moment arms of the extensor carpi radialis longus and brevis tendons again decreased significantly during wrist flexion-extension. The moment arms of the flexor carpi radialis and extensor carpi radialis brevis tendons increased significantly during radioulnar deviation, whereas those of the wrist motors on the ulnar side decreased. These findings indicate the importance of the integrity of the scaphoid in maintaining normal biomechanics of motor tendons of the wrist. An increase in the moment arm of the radial wrist flexor along with a decrease in moment arms of the radial extensors constitutes as etiology for persistent angulation of the scaphoid and the humpback deformity. In addition, disturbing the biomechanics of the wrist motor tendons predisposes the carpal joints to abnormal loading, potentially contributing to the development of carpal joint degeneration.

Carpal instability in the weight-bearing upper extremity

The prevalence of carpal instability in a paraplegic population was investigated to establish an association between chronic repetitive stress on the wrist and the development of such instability. Nine of 162 paraplegic patients had static carpal instability and no history of an acute injury of the wrist. The predominant pattern of instability, found in eleven wrists (six patients), was non-dissociative volar intercalated segmental instability. The prevalence of carpal instability increased with the duration of weight-bearing on the upper extremity. Eighteen per cent of the patients in whom the spinal cord injury had occurred more than twenty years before the study had carpal instability. Carpal instability in these weight-bearing upper extremities and the increase in its prevalence with the duration of the forces across the wrist demonstrate an association between chronic repetitive stress on the wrist and carpal instability.

Radiographic progression to dorsal intercalated segment instability

We present a case of an acute hyper-extension wrist injury that progressed from normal carpal alignment to dorsal intercalated segment instability over a short period of time. Disruption of the scapholunate interosseous and radioscapholunate ligaments was proven arthroscopically, while the intercapsular ligaments were demonstrated to be intact. We have shown that lunate malalignment can occur over time, as secondary lunate ligamentous supports attenuate under abnormal carpal kinetics.

Post-traumatic irreducible nondissociative carpal instability: a case report

We present a case that is unusual in two respects. To our knowledge, it is the first clearly documented instance in the literature of a post-traumatic, irreducible nondissociative volar intercalated carpal instability to result from a known wrist flexion force and a known dorsal capsuloligamentous tear. Second, the same wrist revealed a coalition at both intraosseous levels of the proximal carpal row: a synfibrosis at the scapholunate joint and a synostosis at the lunotriquetral joint. Treatment by open removal of an interposed capsuloligamentous flap from the radiocarpal joint, followed by alignment of carpal elements, temporary internal fixation, and repair of the damaged dorsal capsule and ligaments gave an excellent result.

Wrist kinematics. Row, column or both?

Analysis of radiographs of 52 wrists showed that, from ulnar to radial deviation, the amount of scaphoid shortening and ulnar translation of the scaphoid varies in a normal distribution. There is a significant correlation between the two measurements, such that the more the scaphoid shortens the less it translates and vice versa. Females subjects were more likely to have greater scaphoid shortening and less translation. It is felt that carpal kinematics thus cover a spectrum from the "row" theory to the "column" theory which is normally distributed and that women are more likely to have a column type wrist. This variation may affect the result of treatment of scapholunate dissociation by techniques such as scapho-lunate fusion. A "CR index" is proposed so that the tendency of a wrist towards row or column theory can be quantified. This may be used to predict the success of some surgical procedures in the treatment of scapho-lunate dissociation.

Clinical provocative tests used in evaluating wrist pain: a descriptive study

The purposes of this clinical study were to standardize the method of examination and provocative testing of painful wrists and to compare retrospectively the results of these tests with the arthroscopic findings of three independent hand surgeons. This article operationally defines the scaphoid shift test (SST), the ballottement test (BALLOT), and the ulnomeniscotriquetral dorsal glide test (UMTDG); describes the clinical and arthroscopic examination method; and analyzes the sensitivities, specificities, and predictive values of these provocative tests relative to the arthroscopic findings in 50 painful wrists. Each patient had unspecified wrist pain of at least 4 weeks' duration and was examined by one certified hand therapist who carried out all of the clinical provocative tests. The sensitivities for the SST, the BALLOT, and the UMTDG were 69%, 64%, and 66%, respectively. The specificities for the SST, the BALLOT, and the UMTDG were 66%, 44%, and 64%, respectively. The positive predictive values for the SST, the BALLOT, and the UMTDG were 48%, 24%, and 58%, respectively. The negative predictive values for the SST, the BALLOT, and the UMTDG were 78%, 81%, and 69%, respectively. These wrist provocative tests were efficient for identifying patients who needed a more detailed diagnostic workup and possible arthroscopic inspection. Of those patients who needed arthroscopic inspection, the provocative tests proved to be more efficient at predicting the absence of injury than at predicting its presence.

Determination of wrist kinematics using a magnetic tracking device

The objective of this work is to present a method to determine the three-dimensional kinematics of the human wrist joint under physiological loading conditions using a magnetic tracking device. Euler angles were used to determine wrist extension-flexion, radial-ulnar deviation and supination-pronation. The screw displacement axis (SDA) method was used to describe the relative motion between carpal bones. Computer graphics were also used to obtain a better visualization of the three-dimensional motions of the carpal bones. This was accomplished by combining motion data and digitization data describing the geometry of the articular surfaces of the carpal bones. Geometric data included the locations of several points located on the articular surfaces forming the radio-scaphoid and radio-lunate joints. The SDA axes describing the motions of the capitate or the lunate or the scaphoid with respect to the radius during flexion-extension were found almost parallel to the medial-lateral direction. Translations along any SDA did not exceed 2 mm. One can thus consider the motion of each carpal bone as a pure rotation about a screw axis. Also, the SDA axis describing the motion of the capitate with respect to the radius was found to pass through the proximal end of the capitate. The graphical display of carpal motions shows that, as the wrist is flexed, the surface of the lunate within the radio-lunate articulation moves from palmar to dorsal. On the other hand, the palmar-dorsal location of the proximal surface of the scaphoid within the radio-scaphoid articulation remains almost unchanged.

Chronic lunotriquetral instability: diagnosis and treatment

Fourteen patients with chronic lunotriquetral instability were evaluated. Forced wrist extension was the most common mechanism of injury. Fourteen patients underwent lunotriquetral arthrodesis. Arthrograms were positive in 9 of the 12 performed. In three cases abnormalities not identified by arthrography were demonstrated by arthroscopy. The follow-up period averaged 27 months. X-ray films showed fusion in 12 cases. One pseudarthrosis was asymptomatic. A second pseudarthrosis required a rearthrodesis that became solid 8 weeks after surgery. One patient had persistent wrist pain. Wrist motion compared to the contralateral side averaged 85%, 88%, 83% and 80%, respectively, for flexion, extension, ulnar deviation, and radial deviation. Grip strength compared to the contralateral side averaged 93%. Lunotriquetral instability is a clinical diagnosis confirmed by arthrography or arthroscopy. Lunotriquetral fusion reliably relieves pain while maintaining functional wrist motion and grip strength. The long-term effects of lunotriquetral fusion on carpal kinematics and wrist function are unknown.

Kinematic analysis of relative motion within the proximal carpal row

The motions of the scaphoid and triquetrum relative to the lunate have been studied on cadaver specimens. The helical axis concept was applied. The wrist motions performed were flexion-extension and radial-ulnar deviation. The results showed increased relative motion of the scaphoid towards terminal extension, and to a lesser amount in the case of the triquetrum, towards terminal flexion. The lunate might be considered as a keystone in the proximal carpal row when wrist stability is considered. It is doubly intercalated: longitudinally and transversely. Wrist ligaments co-ordinate the positioning of the bones in the mid-range of carpal motions, and restrict further motion in extreme positions of the wrist joint.

Kinematics of the wrist and its ligaments

Precise anatomic dissections of unembalmed physiologically intact cadaver specimens were carried out before proceeding with the kinematic investigations on further specimens. Carpal flexor and extensor tendons were used to move the wrist. The analysis of the carpal bone movements was performed according to the finite helical axis motion concept for increments of 10 degrees for each main carpal motion. Separate axes of rotation for each of the bones in the proximal carpal row were found; however, the axes for the lunate and triquetrum bones were close, and the magnitudes of rotation and translation almost equal. One finding was that the axes of rotation of the bones in the proximal carpal row often cross at some particular point. Because the axes of the scaphoid are differently oriented than those of the lunate and triquetrum, shear might occur during wrist motion. This indicates also that the scaphoid and lunate cannot be considered rigidly coupled elements. We also assume that the individual bones of the proximal carpal row self-align themselves as long as they are not constrained by torsion. Several potential mechanisms of flexion motion of the proximal carpal row during radioulnar deviations of the hand were considered. The ligament function is still an unsolved problem. Compensation mechanisms may mask clear correlations between a lesion and the instability pattern associated with it. The proximal carpal row should be studied as one system.